发表机构
Laboratoire de Physique des Solides - UMR 8502, CNRS, Université Paris-Saclay; Institut Charles Sadron, Université de Strasbourg & CNRS（巴黎萨克雷大学固体物理实验室; 斯特拉斯堡大学夏尔·萨德龙研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
针对半刚性聚合物液晶，发展第二维里理论并借助分子动力学模拟，揭示瞬态螺旋构象可导致链刚化及对映体形状，并识别弱与强对映异构区域及其交叉条件。
AI 中文摘要
弱柔性、定向聚合物可以呈现潜在无限多样的构象，其中一些具有手性。我们基于链不具有内在分子手性但可呈现任意手性的弱螺旋构象这一假设，发展了一种针对嵌入向列环境中的半刚性聚合物的第二维里理论。我们展示了如何利用这些瞬态螺旋涨落来预测由分子拥挤引起的链刚化程度。理论预测与具有可调主链柔性的珠簧聚合物的大规模分子动力学模拟结果高度一致。尽管理论和模拟都排除了仅由链构象自发产生全局手性对称破缺的可能性，但它们确实揭示了聚合物可以发展出显著的对映体形状。半刚性聚合物的向列流体可以被视为由瞬态螺旋聚合物组成的、对映体过量零的补偿性胆甾相。通过量化在宽浓度和持续长度范围内发展的补偿手性有序程度，可以识别出弱对映异构和强对映异构两个不同区域。当链的持续长度降至约轮廓长度的三倍以下时，两者之间发生交叉。
英文摘要
Weakly flexible, directed polymers can adopt a potentially infinite variety of conformations, some of them chiral. We develop a second-virial theory for semi-rigid polymers embedded in a nematic environment based on the assumption that the chains possess no intrinsic molecular chirality but can take on weakly helical conformations of either handedness. We demonstrate how these transient helical fluctuations can be exploited to predict the degree of chain stiffening induced by molecular crowding. The theoretical predictions are in good agreement with large-scale molecular dynamics simulations of bead-spring polymers with tunable backbone flexibility. Although both theory and simulations rule out spontaneous global chiral symmetry breaking imparted by chain conformations alone, they do reveal that polymers can develop pronounced enantiomeric shapes. Nematic fluids of semi-rigid polymers can be viewed as compensated cholesterics composed of transiently helical polymers with zero enantiomeric excess. By quantifying the degree of compensated chiral order developed over a broad range of concentrations and persistence lengths, two distinct regimes of weak and strong enantiomerism can be identified. A crossover between the two occurs when the chain persistence length drops below roughly three times the contour length.
Comments13 pages, 10 figures
